1. Field of the Invention
This invention relates to a legged walking robot, more particularly to a foot structure of a legged walking robot that effectively absorbs and mitigates shock during walking.
2. Description of the Related Art
Various foot structures have been developed for legged walking robots, particularly for biped walking robots. These include, for example, the structures disclosed by this applicant in Japanese Laid-open Patent Application Nos. Hei. 3(1991)-184781 and Hei. 11(1999)-33941.
The feet of a legged walking robot, particularly those of a biped walking robot, should preferably have an appropriate degree of elasticity for absorbing and mitigating shock at footfall (landing of foot on floor or ground) but also have an appropriate degree of rigidity for maintaining attitude stability after footfall. These properties are, however, incompatible and difficult to achieve simultaneously. The prior art, therefore, has room for improvement regarding this point.
An object of the invention is, therefore, to overcome this problem of the prior art by providing a legged walking robot particularly, a biped walking robot, having a foot structure which enables it to achieve an optimum balance between absorption/mitigation of shock at footfall and attitude stabilization after footfall.
For realizing this object, the invention provides a legged walking robot having at least a body and a plurality of legs each connected to the body and each having a foot at its free end such that the robot is controlled to walk by landing a heel of the foot first on a floor, wherein the improvement comprises: the heel of the foot is constituted of a first member made of a rigid material and a second member made of a rigid material, and the second member is constituted to have a first rigidity against forces acting in a direction of gravity axis and a second rigidity, which is lower than the first rigidity, against forces acting in a direction other than the direction of gravity axis, when the heel is landed.